Petrolisthes virgilius, Hiller, Alexandra & Werding, Bernd, 2019

Hiller, Alexandra & Werding, Bernd, 2019, A new species of Petrolisthes (Crustacea, Anomura, Porcellanidae) inhabiting vermetid formations (Mollusca, Gastropoda, Vermetidae) in the southern Caribbean Sea, ZooKeys 876, pp. 143-151 : 143

Petrolisthes virgilius sp. nov. Figs 2 , 3 a–e

Petrolisthes tonsorius Werding, 1978: 220 (not P. tonsorius Haig, 1960: 85-88)

Material.

Holotype: male, INV CRU8404, Colombia, Chocó, Gulf of Urabá, Triganá, Napú, coll. J. Lazarus, 05 Dec. 2010; 4.6 × 4.5 mm.

Paratypes: 2 males, 2 females (1 ovigerous), INV CRU8405, same collection data as holotype. Size of males is 4.2 × 3.7 mm and 3.3 × 3.2 mm; size of females is 5.3 × 5.2 mm (ovigerous) and 4.3 × 4.0 mm ( Fig. 3 ).

Sizes of largest male and female reported by Werding (1978) are, respectively, 8.0 × 8.1 mm and 6.5 × 6.1 mm.

Diagnosis.

Carapace subquadrate, its margins subparallel posterior to epibranchial angle, nearly smooth, covered anteriorly with few flattened granules; no epibranchial spine; front narrow, triangular, with deep median groove; carpus 1½ times as long as wide, surface granulate, anterior margin with a broad, rounded lobe, separated through an indentation from a shallow distal lobe; manus with a longitudinal ridge; fingers blunt, outer margin convex, forming a rounded crest along entire length; merus of walking legs unarmed.

Description.

Carapace about as long as broad, subquadrate, lateral margins subparallel posterior to epibranchial angles; nearly smooth, covered anteriorly with few flattened granules and posteriorly with light plications; grooves marking the various regions distinct. No epibranchial spine. Front narrow, triangular, strongly produced, with a deep median groove extending between protogastric lobes; no supraocular spine; inner orbital angle not produced. Orbits rather shallow; outer orbital angle produced into a small tooth. Eyes moderately large. Carapace naked. Basal segments of antennae thick, granulate, first movable segments with a marked crest produced to distal edge, second massive and cylindrical, flagellum about 1½ as long as carapace.

Chelipeds broad, naked, covered with small flattened granules on dorsal surface, smooth ventrally. Merus with a small granular lobe on anterior margin, inner distal edge not produced. Carpus ca. 1½ times as long as broad, surface granulate, anterior margin produced into a broad, rounded lobe extending 2/3 of its length, and separated through an indentation from a shallow distal lobe; dorsal surface with a broad, longitudinal ridge. Posterior border convex, forming a granulate crest, ending distally in a rounded tooth. Chelae subequal, moderately large. Manus with a longitudinal ridge. Fingers blunt, pollex frequently longer than dactylus, outer margin convex, forming a rounded crest along entire length; dactylus longitudinally notched. Gape without pubescence.

Walking legs compact, with scattered simple setae. Merus unarmed, broad, flattened; carpus and propodus naked, crested above, dactylus with four movable spinules on inner border.

Telson with seven plates.

Coloration.

The overall coloration of P. virgilius sp. nov. is pale brown to beige, the brown coloration prevailing on chelipeds and frontal half of carapace ( Fig. 2 ). Carpus and manus of chelipeds frequently show scattered, dark-brown spots.

Ecology.

Petrolisthes virgilius sp. nov. was found exclusively in intertidal formations of vermetid snails exposed to strong waves. The new species shares this habitat with Neopisosoma angustifrons (Benedict, 1901), N. neglectum Werding, 1986, and Clastotoechus nodosus (Streets, 1872). The latter species can also be found in other intertidal fouling incrustations in heavily wave-exposed rocky shores ( Werding 1986).

Distribution.

Colombia, Santa Marta and Gulf of Urabá regions.

Etymology.

The new species is named after Dr. Virgilio Galvis Ramírez MD for his support and interest in our research on marine crabs, and for his contributions to medical sciences in Colombia.

Molecular analysis.

The 496 bp alignment consisting of seven 16S rDNA sequences of Petrolisthes virgilius and two of P. tonsorius revealed two haplotypes within the new species, which differ only by one nucleotide. One haplotype was more frequent than the other and was shared by two individuals from Santa Marta and three from the Gulf of Urabá. The other haplotype was shared by two individuals from Santa Marta. The average of genetic distance within the new species was 0.2%. Distances between P. virgilius and P. tonsorius ranged between 9.6% and 10.2%. The average distance between populations of P. tonsorius from the Pacific and Caribbean was 4.8%.

Remarks.

Petrolisthes virgilius can be distinguished morphologically from P. tonsorius and similar species by the marked granulation of carapace and extremities, the marked indentation of the anterior margin of the cheliped’s carpus, and the accentuated crests of the chelipeds.

Figures

Figure 2. Petrolisthes virgilius sp. nov., Colombia, Santa Marta. Scale bar: 2.4 mm.

Figure 3. Petrolisthes virgilius sp. nov., female (ovigerous) paratype, INV-CRU 8405, Colombia, Choco, Gulf of Uraba, Trigana, Napu. a Dorsal view b rostrum, frontal view c orbit with basal segments of antenna d basal segment of antennular peduncle e dactylus of last right walking leg. Scale bars: 5.0 mm (a); 1.0 mm (b-e).